U.S. patent number 9,794,803 [Application Number 14/157,212] was granted by the patent office on 2017-10-17 for system and methods of dynamic tdd configurations.
This patent grant is currently assigned to MEDIATEK INC.. The grantee listed for this patent is MEDIATEK, INC.. Invention is credited to Chien-Hwa Hwang, Shiang-Jiun Lin, Xiangyang Zhuang.
United States Patent |
9,794,803 |
Lin , et al. |
October 17, 2017 |
**Please see images for:
( Certificate of Correction ) ** |
System and methods of dynamic TDD configurations
Abstract
Solutions to support the coexistence of legacy UEs and new
released UEs in adaptive TDD systems are proposed. Methods of TDD
grouping, RACH (random access channel) resource allocation, and
DL/UL data transmission and HARQ (Hybrid Automatic Repeat Request)
process to serve legacy UEs without interfering the operation of
new released UEs are proposed. With the methods proposed in this
invention, both the legacy UEs and the new released UEs can be
served in the adaptive TDD systems and the data transmission from
the legacy UEs would not interfere the data reception of the new
released UEs.
Inventors: |
Lin; Shiang-Jiun (Hsinchu,
TW), Hwang; Chien-Hwa (Hsinchu, TW),
Zhuang; Xiangyang (Lake Zurich, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
MEDIATEK, INC. |
Hsin-Chu |
N/A |
TW |
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Assignee: |
MEDIATEK INC.
(TW)
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Family
ID: |
51207593 |
Appl.
No.: |
14/157,212 |
Filed: |
January 16, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140204783 A1 |
Jul 24, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61754201 |
Jan 18, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
24/02 (20130101); H04L 5/1438 (20130101); H04W
72/048 (20130101); H04L 5/1469 (20130101); H04L
1/1854 (20130101); H04W 74/006 (20130101); H04L
1/1825 (20130101); H04W 48/12 (20130101); H04W
72/1289 (20130101) |
Current International
Class: |
H04W
24/02 (20090101); H04W 72/04 (20090101); H04L
5/14 (20060101); H04L 1/18 (20060101); H04W
72/12 (20090101); H04W 74/00 (20090101); H04W
48/12 (20090101) |
Field of
Search: |
;370/280,252 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102832989 |
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Dec 2012 |
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CN |
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102843732 |
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Dec 2012 |
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CN |
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WO2012106840 |
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Aug 2012 |
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WO |
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WO2012122919 |
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Sep 2012 |
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WO |
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Other References
EPO, Search Report for the EP patent application 14740544.3 dated
Oct. 29, 2015 (17 pages). cited by applicant .
3GPP TSG-RAN WG1 Meeting #69 R1-122363, Renesas Mobile Europe Ltd.,
Discussion on Enhancements for Dynamic TDD UL-DL Configuration,
Prague, Czech Republic dated May 21-25, 2012 (4 pages). cited by
applicant .
3GPP TS 36.211 V11.1.0 (Dec. 2012), 3rd Generation Partnership
Project; technical Specification Group Radio access Network;
Evolved Universal terrestrial Radio Access (E-UTRA); Physical
Channels and Modulation (Release 11) *sections 4 2, 5.7.1*, *tables
4.2-2*, *table 5.7.1-4*. cited by applicant .
International Search Report and Written Opinion of International
Search Authority for PCT/CN2014/070797 dated Apr. 30,2014 (13
pages). cited by applicant.
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Primary Examiner: Thier; Michael
Assistant Examiner: Islam; Rownak
Attorney, Agent or Firm: Imperium Patent Works Jin;
Zheng
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. .sctn.119 from
U.S. Provisional Application No. 61/754,201, entitled "System and
Methods of Dynamic TDD configurations" filed on Jan. 18, 2013, the
subject matter of which is incorporated herein by reference.
Claims
What is claimed is:
1. A method comprising: determining a time division duplex (TDD)
group by a base station in a mobile communication network, wherein
the TDD group contains multiple TDD configurations; broadcasting a
TDD reference configuration of the TDD group to a first UE via a
system information block (SIB), wherein the first UE is a legacy
UE, the TDD reference configuration belongs to the TDD group, the
TDD reference configuration has the most/least common uplink
subframes in the TDD group, wherein the TDD reference configuration
is taken as a common configuration representing all the TDD
configuration of the TDD group, and the TDD reference configuration
of the TDD group is recognized by the first UE as an operating TDD
configuration; and transmitting an instantaneous TDD configuration
to a second UE, wherein the instantaneous TDD configuration belongs
to the TDD group, wherein the second UE is a new-released UE that
supports dynamic TDD adaptation, and wherein the TDD reference
configuration does not change with the changes of the instantaneous
TDD configuration.
2. The method of claim 1, wherein a radio frame contains ten
downlink and uplink subframes #0 to #9, and wherein the multiple
TDD configurations in the same TDD group have common subframes no
less than subframes #0, #1, #2 and #5.
3. The method of claim 1, further comprising: changing to a second
instantaneous TDD configuration within the same TDD group without
changing the TDD reference configuration.
4. The method of claim 1, further comprising: broadcasting a second
TDD reference configuration to the first UE via the SIB, wherein
the second TDD reference configuration belongs to a second TDD
group; and changing to a second instantaneous TDD configuration
that belongs to the second TDD group.
5. The method of claim 1, further comprising: allocating random
access resource in a specific UL subframe for the first UE, wherein
the specific UL subframe is a common UL subframe to all multiple
TDD configurations in the TDD group.
6. The method of claim 1, wherein a legacy information element (IE)
in the SIB is used to broadcast the TDD reference configuration for
legacy UEs.
7. The method of claim 1, wherein a legacy random access resource
configuration information element (IE) is used for legacy UEs, and
wherein an extended random access configuration IE is used for
new-released UEs.
8. The method of claim 1, further comprising: scheduling downlink
(DL) data transmission in a DL subframe such that a corresponding
hybrid automatic repeat request (HARQ) feedback for the DL data
transmission is transmitted in a common UL subframe of the TDD
group.
9. The method of claim 1, further comprising: allocating an UL
grant in a DL subframe for UL data transmission such that UL data
is transmitted in a common UL subframe of the TDD group.
10. The method of claim 1, further comprising: scheduling UL data
transmission in a UL subframe such that a corresponding hybrid
automatic repeat request (HARQ) feedback for the UL data
transmission is transmitted in a common DL subframe.
11. The method of claim 10, further comprising: suppressing UL
retransmission if the UL retransmission may happen in an
inconsistent subframe.
12. A method comprising: receiving a TDD reference configuration of
a TDD group by a user equipment (UE), wherein the TDD group
contains multiple TDD configurations and the TDD reference
configuration belongs to the TDD group and the TDD reference
configuration has the most/least common uplink subframes in the TDD
group, wherein the TDD reference configuration is taken as a common
configuration representing all the TDD configuration of the TDD
group; and performing measurements based on the TDD reference
configuration of the TDD group if the UE is a legacy UE, wherein
the TDD reference configuration of the TDD group is recognized by
the UE as an operating TDD configuration, wherein the UE performs
measurements based on an instantaneous TDD configuration if the UE
is a new-released UE that supports dynamic TDD adaptation, wherein
the TDD reference configuration does not change with the changes of
the instantaneous TDD configuration.
13. The method of claim 12, wherein a radio frame contains ten
downlink and uplink subframes #0 to #9, and wherein the multiple
TDD configurations in the same TDD group have common subframes no
less than subframes #0, #1, #2 and #5.
14. The method of claim 12, wherein the UE obtains the TDD
reference configuration from a legacy information element (IE) in a
system information block (SIB) if the UE is the legacy UE.
15. The method of claim 12, wherein the UE reads a legacy random
access resource configuration information element (IE) for random
access if the UE is the legacy UE, and wherein the UE reads an
extended random access configuration IE for random access if the UE
is the new-released UE.
16. A user equipment (UE) comprising: a receiver that receives a
TDD reference configuration of a TDD group, wherein the TDD group
contains multiple TDD configurations and the TDD reference
configuration belongs to the TDD group and the TDD reference
configuration has the most/least common uplink subframes in the TDD
group, wherein the TDD reference configuration is taken as a common
configuration representing all the TDD configuration of the TDD
group; and a measurement module that performs measurements based on
the TDD reference configuration of the TDD group if the UE is a
legacy UE, wherein the TDD reference configuration of the TDD group
is recognized by the UE as an operating TDD configuration, wherein
the measurement module performs measurements based on an
instantaneous TDD configuration if the UE is a new-released UE that
supports dynamic TDD adaptation, wherein the TDD reference
configuration does not change with the changes of the instantaneous
TDD configuration.
17. The UE of claim 16, wherein a radio frame contains ten downlink
and uplink subframes #0 to #9, and wherein the multiple TDD
configurations in the same TDD group no less than common subframes
than subframes #0, #1, #2 and #.
18. The UE of claim 16, wherein the UE obtains the TDD reference
configuration from a legacy information element (IE) in a system
information block (SIB) if the UE is the legacy UE.
19. The UE of claim 16, wherein the UE reads a legacy random access
resource configuration information element (IE) for random access
if the UE is the legacy UE, and wherein the UE reads an extended
random access configuration IE for random access if the UE is the
new-released UE.
Description
TECHNICAL FIELD
The present invention relates generally to wireless communication
systems and, more particularly, to dynamic Time Division Duplex
(TDD) configurations in LTE systems.
BACKGROUND
In wireless communication systems, such as defined by 3GPP Long
Term Evolution (LTE/LTE-A) specification, user equipments (UE) and
base stations (eNodeB) communicate with each other by sending and
receiving data carried in radio signals according to a predefined
radio frame format. Typically, the radio frame format contains a
sequence of radio frames, each radio frame having the same frame
length with the same number of subframes. The subframes are
configures to perform uplink (UL) transmission or downlink (DL)
reception in different Duplexing methods. Time-division duplex
(TDD) is the application of time-division multiplexing to separate
transmitting and receiving radio signals. TDD has a strong
advantage in the case where there is asymmetry of the uplink and
downlink data rates. Seven different TDD configurations are
provided in LTE/LTE-A systems to support different DL/UL traffic
ratios for different frequency bands.
FIG. 1 (Prior Art) illustrates the TDD mode UL-DL configurations in
an LTE/LTE-A system. Table 100 shows that each radio frame contains
ten subframes, D indicates a DL subframe, U indicates an UL
subframe, and S indicates a Special subframe/Switch point (SP).
Each SP contains a DwPTS (Downlink pilot time slot), a GP (Guard
Period), and an UpPTS (Uplink pilot time slot). DwPTS is used for
normal downlink transmission and UpPTS is used for uplink channel
sounding and random access. DwPTS and UpPTS are separated by GP,
which is used for switching from DL to UL transmission. The length
of GP needs to be large enough to allow the UE to switch to the
timing advanced uplink transmission. These allocations can provide
40% to 90% DL subframes. Current UL-DL configuration is broadcasted
in the system information block, i.e. SIB1. The semi-static
allocation via SIB1, however, may or may not match the
instantaneous traffic situation. Currently, the mechanism for
adapting UL-DL allocation is based on the system information change
procedure.
In 3GPP LTE Rel-12 and after, the trend of the system design shows
the requirements on more flexible configuration in the network
system. Based on the system load, traffic type, traffic pattern and
so on, the system can dynamically adjust its parameters to further
utilize the radio resource and to save the energy. One example is
the support of dynamic TDD configuration, where the TDD
configuration in the system may dynamically change according to the
DL-UL traffic ratio. When the change better matches the
instantaneous traffic situation, the system throughput will be
enhanced. For example, in one scenario, multiple indoor Femto cells
deployed on the same carrier frequency and multiple Macro cells
deployed on an adjacent carrier frequency where all Macro cells
have the same UL-DL configuration and the indoor Femto cells can
adjust UL-DL configuration. In another scenario, multiple outdoor
Pico cells deployed on the same carrier frequency and multiple
Macro cells deployed on an adjacent carrier frequency where all
Macro cells have the same UL-DL configuration and the outdoor Pico
cells can adjust UL-DL configuration.
FIG. 2 (Prior Art) illustrates an LTE/LTE-A mobile communication
system 200 with adaptive TDD configuration. Mobile communication
system 200 comprises a Macro base station eNB 201 serving Macro
cell 1, base station eNB 202 serving small cell 2, and base station
eNB 203 serving small cell 3. Cell 1 is a Macro cell and its TDD
configuration is more static. Small Cells 2-3 are within the macro
cell's coverage. Cell 2 and Cell 3 form an isolated cell cluster 1,
where TDD configuration can be independently adjusted. All cells in
an isolated cell cluster should apply the TDD configuration change
together. In this example, assume cell 1 applies TDD configuration
5, which is configured semi-statically, and the isolated cell
cluster, i.e. cell 2 and cell 3, originally applies TDD
configuration 5. As more UL traffic is demanded in the isolated
cluster, it changes the TDD configuration to TDD configuration
3.
The notification of TDD change in an adaptive TDD system may be
sent through a dedicated signaling, i.e., RRC (Radio Resource
Control), MAC (Media Access Control), or PDCCH (Physical Downlink
Control Channel) signaling. One reason to adopt TDD configuration
change by dedicated signaling is that it can be adjusted more
efficiently and frequently to match the instantaneous traffic
pattern. In an adaptive TDD system, however, there may be legacy
UEs and new released UEs. If the TDD change is sent through the
dedicated signaling, then only new released UEs understand the
information. The legacy UEs cannot know the dynamic TDD
configuration because they cannot interpret the new information
element. As a result, the legacy UEs may interfere with the
operation of other UEs. For example, a legacy UE3 may perform
random access in its cognitive UL subframe, but the subframe is
operated for DL transmission due to the TDD configuration
change.
A solution is sought.
SUMMARY
Solutions to support the coexistence of legacy UEs and new released
UEs in adaptive TDD systems are proposed. Methods of TDD grouping,
RACH (random access channel) resource allocation, and DL/UL data
transmission and HARQ (Hybrid Automatic Repeat Request) process to
serve legacy UEs without interfering the operation of new released
UEs are proposed. With the methods proposed in this invention, both
the legacy UEs and the new released UEs can be served in the
adaptive TDD systems and the data transmission from the legacy UEs
would not interfere the data reception of the new released UEs.
In a first solution, TDD grouping methods, TDD adaptation within a
TDD group, and TDD adaptation across TDD groups for the operation
of a dynamic TDD system are proposed. In one embodiment, an eNB
configures TDD groups and broadcasts TDD group information and a
TDD reference configuration to UEs. A TDD group contains multiple
TDD configurations that have common subframes no less than
subframes #0, #1, #2 and #5. The TDD reference configuration
belongs to the TDD group and has the most common uplink (UL)
subframes as compared to other TDD configurations in the TDD
group.
In a second solution, since the legacy UEs' cognition on DL/UL
operation in a subframe may be different from real operation in a
dynamic TDD system, the PRACH resource configuration and the random
access procedure for the legacy UEs are proposed. In one
embodiment, PRACH resource allocation is restricted to subframes
that are commonly used as UL operation in a TDD group. In another
embodiment, TDD configuration and PRACH resource configuration are
extended in SIB1 and SIB2 to serve both legacy UEs and new released
UEs so that PRACH resource allocation is not limited.
In a third solution, methods of DL/UL data transmission scheduling
and the associated HARQ for DL/UL data transmission scheduling for
the legacy UEs are proposed. For DL data transmission, eNB should
schedule DL transmission or retransmission in a DL subframe where
its corresponding HARQ feedback should be transmitted in a common
UL subframe. For UL data transmission, eNB should allocate UL grant
in a DL subframe where the UL data should be transmitted in a
common UL subframe. For HARQ feedback for UL data transmission, the
DL subframes used to transmit the HARQ feedback should be common DL
subframes. Finally, eNB can suppress UL retransmission so that it
does not happen in inconsistent subframes.
Other embodiments and advantages are described in the detailed
description below. This summary does not purport to define the
invention. The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, where like numerals indicate like
components, illustrate embodiments of the invention.
FIG. 1 (Prior Art) illustrates the TDD mode UL-DL configurations in
an LTE/LTE-A system.
FIG. 2 (Prior Art) illustrates an LTE/LTE-A mobile communication
system with adaptive TDD configuration.
FIG. 3 illustrates an LTE/LTE-A mobile communication system with
adaptive TDD configuration in accordance with one novel aspect.
FIG. 4 is a simplified block diagram of a user equipment and a base
station with adaptive TDD in accordance with one novel aspect.
FIG. 5 illustrates a first embodiment of TDD grouping in an
adaptive TDD system.
FIG. 6 illustrates a second embodiment of TDD grouping in an
adaptive TDD system.
FIG. 7 illustrates a third embodiment of TDD grouping in an
adaptive TDD system.
FIG. 8 illustrates a solution of broadcasting TDD grouping and TDD
configuration change procedure.
FIG. 9 illustrates one embodiment of RACH resource allocation in an
adaptive TDD system.
FIG. 10 illustrates TDD and RACH resource configuration extension
in SIB.
FIG. 11A illustrates Downlink data transmission scheduling and HARQ
for DL transmission.
FIG. 11B illustrates HARQ timing with DL association set index for
TDD.
FIG. 11C illustrates one embodiment of DL data transmission in an
adaptive TDD system.
FIG. 11D illustrates another embodiment of DL data transmission in
an adaptive TDD system.
FIG. 12A illustrates Uplink data transmission scheduling and HARQ
for UL transmission.
FIG. 12B illustrates Uplink grant timing for UL transmission or
retransmission.
FIG. 12C illustrates one embodiment of UL data transmission or
retransmission in an adaptive TDD system.
FIG. 12D illustrates another embodiment of UL data transmission or
retransmission in an adaptive TDD system.
FIG. 13A illustrates the timing of HARQ feedback for UL data
transmission.
FIG. 13B illustrates one embodiment of HARQ scheduling for UL
transmission in an adaptive TDD system.
FIG. 13C illustrates another embodiment of HARQ scheduling for UL
transmission in an adaptive TDD system.
FIG. 13D illustrates UL data retransmission in an adaptive TDD
system.
FIG. 14 is a flow chart of a method of adaptive TDD configuration
from eNB perspective in accordance with one novel aspect.
FIG. 15 is a flow chart of a method of adaptive TDD configuration
from UE perspective in accordance with one novel aspect.
DETAILED DESCRIPTION
Reference will now be made in detail to some embodiments of the
invention, examples of which are illustrated in the accompanying
drawings.
FIG. 3 illustrates a Long Term Evolution LTE/LTE-A mobile
communication system 300 with adaptive TDD configuration in
accordance with one novel aspect. Mobile communication system 300
comprises a serving base station eNB 301, a new released UE 302,
and a legacy UE 303. In one example, UE 302 is a UE released
in/after LTE Rel-12, and UE 303 is a UE released before LTE Rel-12.
Starting from LTE Rel-12, adaptive Time Division Duplex (TDD)
transmission mode is supported, where the TDD configuration in the
system may dynamically change according to the downlink-uplink
traffic ratio to better match the instantaneous traffic situation
and thereby enhancing the system throughput.
The notification of TDD change in an adaptive TDD system may be
sent through dedicated signaling, i.e., RRC (Radio Resource
Control), MAC (Media Access Control), or PDCCH (Physical Downlink
Control Channel) signaling. One reason to adopt TDD configuration
change by dedicated signaling is that it can be adjusted more
efficiently and frequently to match the instantaneous traffic
pattern. In an adaptive TDD system, however, there may be legacy
UEs and new released UEs. If the TDD change is sent through the
dedicated signaling, then only new released UEs understand the
information. The legacy UEs cannot know the dynamic TDD
configuration because they cannot interpret the new information
element. The present application proposes solutions for coexistence
of legacy UEs and new released UEs in such adaptive TDD system.
In step 311, the serving eNB 301 sends an instantaneous TDD
configuration to new released UE 302 via dedicated signaling. Based
on the instantaneous TDD configuration, UE 302 knows the exact
DL/UL operation in each subframe, so that all subframes can be used
to serve UE 302. On the other hand, legacy UE 303's knowledge on
the DL/UL operation in each subframe may be different from the real
DL/UL operation, thus only the common subframes can be used to
serve UE 303. To observe the TDD configurations, some subframes are
common in certain TDD configurations, which may be possible to be
used to serve the legacy UEs. A common subframe or a fixed subframe
means no matter how TDD configuration changes, the DL, SP, or UL
operation in such subframe will not be changed. For example,
subframes SF#0, #1, #2, and #5 are common in all TDD
configurations.
In one novel aspect, to obtain more subframes in common, TDD
configurations are partitioned into different TDD groups. In step
312, eNB 301 determines TDD grouping. Based on the TDD grouping,
various solutions are provided to facilitate the coexistence of new
released UE 302 and legacy UE 303. In a first solution (step 321),
different TDD grouping methods, TDD adaptation within a TDD group,
and TDD adaptation across TDD groups for the operation of a dynamic
TDD system are proposed. In a second solution (step 322), since the
legacy UEs' cognition on DL/UL operation in a subframe may be
different from real operation in a dynamic TDD system, the PRACH
resource configuration and the random access procedure for the
legacy UEs are proposed. In a third solution (step 323), methods of
DL/UL data transmission scheduling and the associated HARQ for
DL/UL data transmission scheduling for the legacy UEs are proposed.
With the methods proposed in this invention, both legacy UEs and
new released UEs can be served in the adaptive TDD systems and data
transmission from the legacy UEs would not interfere that of the
data reception of the new released UEs.
FIG. 4 is a simplified block diagram of a base station eNB 401 and
a user equipment UE 402 with adaptive TDD in accordance with one
novel aspect. Base station eNB 401 comprises memory 411, a
processor 412, an RF transceiver 413, and an antenna 419. RF
transceiver 413, coupled with antenna 419, receives RF signals from
antenna 419, converts them to baseband signals and sends them to
processor 412. RF transceiver 413 also converts received baseband
signals from processor 412, converts them to RF signals, and sends
out to antenna 419. Processor 412 processes the received baseband
signals and invokes different functional modules to perform
features in eNB 401. Memory 411 stores program instructions and
data 414 to control the operations of eNB 401. The program
instructions and data 414, when executed by processor 412, enables
eNB 401 to providing TDD information and performing various
functions accordingly.
Similarly, UE 402 comprises memory 421, a processor 422, an RF
transceiver 423, and an antenna 429. RF transceiver 423, coupled
with antenna 429, receives RF signals from antenna 429, converts
them to baseband signals and sends them to processor 422. RF
transceiver 413 also converts received baseband signals from
processor 422, converts them to RF signals, and sends out to
antenna 429. Processor 422 processes the received baseband signals
and invokes different functional modules to perform features in UE
402. Memory 421 stores program instructions and data 424 to control
the operations of UE 402. The program instructions and data 424,
when executed by processor 422, enables UE 402 to access a mobile
communication network for receiving TDD configuration information
and performing various functions accordingly.
FIG. 4 also illustrates various function modules in eNB 401 and UE
402. The different components and modules may be implemented in a
combination of hardware circuits and firmware/software codes being
executable by processors 412 and 422 to perform the desired
functions. For example, eNB 401 includes a scheduler 415 that
schedules DL and UL transmissions for UE, a resource allocation
module 416 that allocates radio resource for UE, a TDD
configuration module 417 that determines TDD grouping and
configuration, and an RRC connection management module 418 that
manages and configures RRC connections. Similarly, UE 402 includes
a transmission and HARQ module 425 that performs DL and UL
transmission and provides HARQ feedback, a random access module 426
that performs random access procedure, a measurement module 427
that performs radio signal measurements, and an RRC connection
management module 428 that performs cell (re)selection and RRC
(re)establishment procedures.
TDD Grouping
FIG. 5 illustrates a first embodiment of TDD grouping in an
adaptive TDD system. In the first embodiment, downlink-to-uplink
switch-point periodicity with 10 ms form a TDD group (TDD Group
#1-1 as depicted by table 501), where subframes SF#0, 1, 2, 5, 6,
7, 8, and 9 are common subframes. Downlink-to-uplink switch-point
periodicity with 5 ms form another TDD group (TDD Group #1-2 as
depicted by table 502), where subframes SF#0, 1, 2, 5, 6, and 7 are
common subframes. By grouping different TDD configurations based on
downlink-to-uplink switch-point periodicity, more common-subframes
are obtained within the same TDD group to serve legacy UEs.
FIG. 6 illustrates a second embodiment of TDD grouping in an
adaptive TDD system. In the second embodiment, downlink-to-uplink
switch-point periodicity with 10 ms form a TDD group (TDD Group
#2-1 as depicted by table 601), where subframes SF#0, 1, 2, 5, 6,
7, 8, and 9 are common subframes. Downlink-to-uplink switch-point
periodicity with 5 ms, excluding TDD configuration #0, form another
TDD group (TDD Group #2-2 as depicted by table 602), where
subframes SF#0, 1, 2, 5, 6, 7, 8, and 9 are common subframes. TDD
configuration #0 forms its own TDD group (TDD Group#2-3 as depicted
by table 603), where all subframes can be used to serve legacy UEs
and new released UEs. It can be seen that, by separating TDD
configuration #0, more common-subframes are obtained for TDD Group
#2-2 as compared to TDD Group #1-2.
FIG. 7 illustrates a third embodiment of TDD grouping in an
adaptive TDD system. In the third embodiment, all seven TDD
configurations #0 to #6 are grouped into one single TDD group (TDD
Group #3-1 as depicted by table 701), where subframes SF#0, 1, 2
and 5 are common subframes. This is an extreme case where the
common subframes of the TDD group are the same with or without TDD
grouping.
In general, with TDD grouping, more common-subframes can be
obtained in a TDD group as compared to without TDD grouping. As a
result, more subframes can be used to serve legacy UEs. In
addition, fewer subframes may change when TDD configurations are
adapted within the same TDD group, which may be beneficial to HARQ
process continuation during the TDD adaptation. Furthermore, TDD
operations in TDD groups may help interference coordination among
neighboring cells. In order to achieve the above benefits, the TDD
grouping information needs to be communicated from the network to
the UEs.
FIG. 8 illustrates a solution of broadcasting TDD grouping and TDD
configuration change procedure. A serving base station eNB 801
first determines TDD grouping, which contains two TDD groups--TDD
group #1 and TDD group #2. In step 810, eNB 801 applies a first TDD
configuration that belongs to TDD group #1. In step 811, eNB 801
sends the first instantaneous TDD configuration to a new released
UE 802 via dedicated signaling. In step 812, eNB 801 sends a TDD
reference configuration of TDD group #1 via broadcasting in System
Information Block (SIB1). The TDD reference configuration belongs
to TDD group #1, and contains the most common uplink subframes as
compared to all other TDD configurations in TDD group #1. For
example, a cell in TDD Group #1-1 should broadcast TDD
configuration #3 as its TDD reference configuration, and a cell in
TDD Group#1-2 should broadcast TDD configuration #0 as its TDD
reference configuration. In a similar example, a cell in TDD Group
#2-1, #2-2, or #2-3 can broadcast TDD reference configuration #3,
#6, or #0 respectively as its TDD reference configuration.
In step 820, eNB 801 applies a second TDD configuration that
belongs to TDD group #1. In step 821, eNB 801 sends the second
instantaneous TDD configuration to the new released UE 802 via
dedicated signaling. Because the second TDD configuration belongs
to the same TDD group #1 broadcasted in SIB1, eNB 801 is able to
adaptively change TDD configuration within the same TDD group
without changing the reference TDD configuration of TDD group #1
broadcasted in SIB1. Later on, eNB 801 decides to change TDD
configuration across TDD groups. If TDD configuration changes
across TDD groups, then the TDD reference configuration in SIB1
should first be changed to be the predefined TDD reference
configuration of the new TDD group. In other words, system
information change procedure should be applied, and then the new
TDD configuration across TDD groups can be applied.
In step 830, eNB 801 decides to apply a third TDD configuration
that belongs to a different TDD group #2. In step 831, eNB 801
sends the third instantaneous TDD configuration to the new released
UE 802 via dedicated signaling. In step 832, eNB 801 sends a TDD
reference configuration of TDD group #2 via broadcasting in SIB1.
The TDD reference configuration belongs to TDD group #2, and
contains the most common uplink subframes as compared to all other
TDD configurations in TDD group #2. In one specific example, a cell
originally operates in TDD Group #2-1 and broadcasts TDD reference
configuration #3 for TDD Group #2-1 in its SIB1. If the cell
decides to change to TDD configuration #2 that belongs to TDD Group
#2-2, then the cell should first apply system information change
procedure to broadcast TDD reference configuration #6 for the new
TDD Group #2-2 in its SIB1, and then change to the new TDD
configuration #2 accordingly.
Random Access
Because a legacy UE does not know the UL/DL change in the network,
it may happen that the legacy UE performs random access in an
operating DL subframe because the cognition on DL/UL of a subframe
for the legacy UE may be different from the real operation. To
prevent the unnecessary preamble transmission from legacy UEs,
which may result in random access failure, and to prevent the
preamble interfering with DL transmission of new released UEs in an
adaptive TDD network, various solutions are proposed. Note that in
LTE, TDD configuration is broadcasted in SIB1 and common PRACH
resource configuration is broadcasted in SIB2.
FIG. 9 illustrates one embodiment of RACH resource allocation in an
adaptive TDD system. In one novel aspect, the random access
resource allocation should be restricted to the subframes that are
commonly used as UL operation in a TDD group. As illustrated in
FIG. 9, for TDD Group #1-1, random access resource can be
configured in subframe SF#2 and/or UpPTS in subframe SF#1. For TDD
Group #1-2, random access resource can be configured in subframes
SF#2, SF#7, and/or UpPTS in subframes SF#1 and SF#6. By restricting
random access resource to common UL subframes within a TDD group,
RACH preambles are always transmitted in an operating UL
subframe.
In another alternative embodiment, the TDD reference configuration
broadcasted in SIB1 should be the TDD configurations containing the
least common UL subframes in a TDD group. This is to guarantee that
random access would not be performed in DL subframes when TDD
configuration is changed. The common PRACH resource is configured
in the UL subframes of the TDD reference configuration broadcasted
in SIB1, and UE performs preamble transmission in theses configured
PRACH resource. In one example, a cell in TDD Group #1-1 should
broadcast TDD configuration #5 in its SIB1 because TDD
configuration #5 is with the least common subframes in TDD Group
#1-1, and a cell in TDD Group #1-2 should broadcast TDD
configuration #2 in its SIB1 because TDD configuration #2 is with
the least common subframes in TDD Group #1-2.
To avoid the PRACH resource limitation, both TDD configuration and
RACH resource configuration can be extended in SIB. FIG. 10
illustrates TDD and RACH resource configuration extension in system
information. As illustrated in FIG. 10, in step 1011, a serving
base station eNB 1001 broadcasts a TDD configuration with the least
common UL subframe in the legacy information element (IE) in SIB1
for a legacy UE 1003, and broadcasts another TDD configuration in
an extended IE in SIB1 for a new released UE 1002. In step 1012,
eNB 1001 broadcasts PRACH resource configuration in the legacy
PRACH-config IE in SIB2 for legacy UE 1003, and broadcasts PRACH
resource configuration in an extended PRACH-config IE in SIB2 for
new released UE 1002. For example, a cell in TDD Group #1-1 may
broadcast TDD configuration #5 in the legacy IE and may broadcast
TDD configuration #3 in an extended IE in SIB1. The PRACH resource
configuration can be extended in SIB2 accordingly. The PRACH
resource configuration in SIB2 should indicate the PRACH resource
for TDD configuration #5 in the legacy IE and indicate the PRACH
resource for TDD configuration #3 in the extended IE. In step 1013,
new released UE 1002 performs random access in the PRACH resource
allocated according to the PRACH configuration in the extended
PRACH-config IE. In step 1014, legacy UE 1003 performs random
access in the PRACH resource allocated according to the PRACH
configuration in the legacy PRACH-config IE. By using both legacy
and extended SIB1 and SIB2, PRACH resource configuration is not
limited for legacy UEs.
Data Transmission and HARQ Process
After random access is successfully performed by a UE, an RRC
connection between the UE and its serving eNB is established. As
stated earlier, the knowledge of TDD configuration for a legacy UE
may not be the same as the exact TDD operation in an adaptive TDD
system. For example, a legacy UE may reply HARQ for DL data
transmission in an operating DL subframe, while the eNB will not
expect HARQ for DL data transmission in a DL subframe and will not
receive this HARQ message so that DL retransmissions may happen. As
to UL transmission, a legacy UE may perform UL data transmission in
an operating DL subframe, while the eNB will not expect to receive
the UL data so UL retransmission may happen. In addition, a UE may
expect HARQ for UL data transmission in a DL subframe. However,
when the TDD configuration changes, the original DL subframe which
is expected to transmit the HARQ for UL data transmission may
become a UL subframe. As a result, the HARQ message will not be
transmitted by the eNB and will not be received by the UE so UL
retransmission may happen. The UL transmission or retransmission
may also interfere the DL reception of nearby UEs. Therefore, DL/UL
Data transmission and the associated HARQ should be considered for
the operation of legacy UEs without changing any specification.
After a serving eNB establishes an RRC connection with a UE, the
eNB can enquiry UE capability to know the UE's release. If the UE's
release version is known by the eNB, then the eNB can prevent
scheduling DL/UL data transmission and/or HARQ for DL/UL data
transmission in the inconsistent subframes (flexible subframes),
where the inconsistent subframe means the legacy UE's cognition on
DL/UL operation in a subframe is different from the real operation.
The following discussions assume that SIB1 broadcasts predefined
TDD reference configuration with the MOST COMMON UL subframes in a
TDD group, and the TDD reference configuration is recognized by
legacy UEs as the operating TDD configuration.
FIG. 11A illustrates Downlink data transmission scheduling and HARQ
for DL transmission. As illustrated in FIG. 11A, an eNB first
schedules DL data transmission or retransmission in a DL subframe
1101 to a UE. The UE should response with HARQ for the DL data
transmission in a corresponding UL subframe 1102. The HARQ timing
is depicted by Table 1110 (e.g., 10.1.3.1-1 in TS 36.213) in FIG.
11B. Table 1110 lists, for each TDD configuration, a specific UL
subframe is used for HARQ for corresponding DL data transmission
that is K subframes ahead of the specific UL subframe. For example,
in TDD configuration #0, UL subframe SF#2 is used for HARQ for K=6
subframes ahead of SF#2 (e.g., DL SF#5). After combining TDD
configuration with HARQ timing for DL data transmission, it can be
determined that the HARQ ACK/NACK for a DL subframe should be
replied in which corresponding UL subframe(s) for each TDD
configuration.
FIG. 11C illustrates one embodiment of DL data transmission in an
adaptive TDD system. In TDD Group #1-1, the knowledge of TDD
configuration for a legacy UE should be TDD configuration #3.
However, the eNB may operate in TDD configurations #3, 4, or 5. For
a legacy UE, to prevent invalid HARQ feedback in inconsistent
subframes, the eNB should schedule DL data
transmission/retransmission in a DL subframe where its HARQ
feedback for DL data transmission should be transmitted in a common
UL subframe. On the other hand, for a new released UE, the DL data
can be scheduled in any DL subframe. Note that common UL subframes
for all TDD configurations in each TDD group are indicated by bold
text and dashed lines.
As depicted by Table 1120 in FIG. 11C, in Group #1-1, the TDD
configuration for legacy UEs is TDD configuration #3. In this case,
eNB should prevent DL data transmission or retransmission
scheduling in subframes SF#0, 7, 8, and 9 (e.g., crossed out in
Table 1120) for a legacy UE. Instead, the eNB can schedule DL data
transmission or retransmission in subframes SF #1, 5, 6 for the
legacy UE and the legacy UE should response the corresponding HARQ
in common UL subframes SF#2. As depicted by Table 1130 in FIG. 11C,
in TDD Group #1-2, the TDD configuration for legacy UEs is TDD
configuration #0. In this case, eNB should prevent DL data
transmission or retransmission scheduling in subframes SF#0 and 5
(e.g., crossed out in Table 1130) for a legacy UE. Instead, the eNB
can schedule DL data transmission or retransmission in subframes
SF#1 and 6 for the legacy UE and the legacy UE should response the
corresponding HARQ in common UL subframes SF#7 and 2,
respectively.
FIG. 11D illustrates another embodiment of DL data transmission in
an adaptive TDD system. Similar concept can be applied in the TDD
Groups #2-2 and #2-3. As depicted by Table 1140 in FIG. 11D, in TDD
Group #2-2, the TDD configuration to legacy UEs is TDD
configuration #6. In this case, eNB should prevent DL data
transmission or retransmission scheduled in subframes SF#1, 6, and
9 (e.g., crossed out in Table 1140) for a legacy UE. Instead, the
eNB can schedule DL data transmission or retransmission in
subframes SF#0 and 5 for the legacy and the legacy UE should
response the corresponding HARQ in UL subframes SF#7 and 2,
respectively. As depicted by Table 1150 in FIG. 11D, in TDD Group
#2-3, since there is only one TDD configuration in this group, the
operation for legacy UEs and new released UEs should be the same
for DL transmission/retransmission.
FIG. 12A illustrates Uplink data transmission scheduling and HARQ
for UL transmission. As illustrated in FIG. 12A, an eNB first
assigns a UL grant in a DL subframe 1201 to a UE. The UE performs
UL data transmission in the assigned UL resource in UL subframe
1202, and then the eNB replies HARQ feedback for the UL data
transmission in a corresponding DL subframe 1203. The UL grant
timing is listed in Table 1210 in FIG. 12B (e.g., Table 8-2 in
36.213). Table 1210 lists, for each TDD configuration, if a UE
receives a UL grant in DL subframe n, then the UL resource should
be in subframe n+k. For example, in TDD configuration #0, if a UE
receives a UL grant in subframe SF#0, then the associated UL
resource is in subframe SF#4. By combing TDD configuration and UL
grant timing, it can be determined a specific DL subframe to be
used to assign a UL grant for uplink data transmission in a
specific UL subframe. For example, in TDD configuration #3, DL
subframe SF#9 may assign UL grant for UL transmission in uplink
SF#3.
In one novel aspect, for a legacy UE, to prevent its UL
transmission interfering other UE's DL operation, eNB should
allocate UL grant in a DL subframe where the UL data should be
transmitted in a common UL subframe. For newly release UE, the UL
grant can be allocated in any DL subframe.
FIG. 12C illustrates one embodiment of UL data transmission
scheduling in an adaptive TDD system. In TDD Group #1-1, an eNB
should prevent allocating UL grant in DL subframes SF#0 and 9 for a
legacy UE, where the corresponding UL transmissions are in
subframes SF#4 and 3, respectively. Instead, the eNB can allocate
UL grant in subframe SF#8 for the legacy UE, where the
corresponding UL transmission should be transmitted in UL subframe
SF#2, as depicted by Table 1220. Similarly, in TDD Group #1-2, the
eNB should prevent UL grant in DL subframes SF#0 and 5 for a legacy
UE, where the corresponding UL transmissions are in subframes SF#4
and 9, respectively. Instead, the eNB can allocate UL grant in DL
subframes SF#1 and 6 for the legacy UE, where the corresponding UL
transmission should be transmitted in UL subframes SF#7 and 2,
respectively, as depicted by Table 1230.
FIG. 12D illustrates another embodiment of UL data transmission
scheduling in an adaptive TDD system. Similar concept can be
applied in TDD Groups #2-2 and 2-3. In TDD Group #2-2, the TDD
configuration for legacy UEs is TDD configuration #6. An eNB should
prevent UL grant in DL subframes SF#1, 6 and 9 for a legacy UE,
where the corresponding UL transmissions are in subframes SF#8, 3
and 4, respectively. Instead, the eNB can allocate UL grant in DL
subframes SF#0 and 5 for the legacy UE, where the corresponding UL
transmission should be transmitted in UL subframes SF#7 and 2,
respectively, as depicted by Table 1240. In TDD Group #2-3, since
there is only one TDD configuration in this group, the operation
for legacy UEs and new released UEs should be the same, as depicted
by Table 1250.
FIG. 13A illustrates the timing of HARQ for UL data transmission,
as indicated in table 1310 (Table 9.1.2-1 in TS 36.213). HARQ
feedback for UL data transmission should be transmitted in DL
subframes. For a legacy UE, eNB should prevent the DL subframes
used to transmit HARQ for UL data transmission may become operating
UL subframes. Fortunately, the legacy UEs operated in the TDD
reference configuration with less common DL subframes in a TDD
group. These common DL subframes, which may use transmit HARQ for
UL data transmission for legacy UEs, will not be operated as UL
subframes. Table 1310 lists the HARQ timing for UL data
transmission. If a UL data transmission happens in subframe n, then
the HARQ associated to the UL data transmission should be in
subframe n+k, where k is the number indicated in the table. For
example, in TDD configuration #1, the HARQ feedback for subframe
SF#2 (n=2) is in the following DL subframe SF#6 (k=4).
FIG. 13B illustrates a first embodiment of HARQ scheduling for UL
data transmission in an adaptive TDD system. In TDD Group #1-1, the
HARQ feedback for UL data transmission for UL subframe SF#2 should
be transmitted in DL subframe SF#8, which is a common DL in the TDD
Group and will not be changed to UL operation, as shown in Table
1320. In TDD Group #1-2, the HARQ feedback for UL data transmission
for UL subframes SF#2 and 7 should be transmitted in the DwPTS in
SF#6 and 1, which is a common special subframe in the TDD Group and
will not be changed as a UL subframe, as shown in Table 1330. Note
that the common DL subframes or common special subframes for all
TDD configurations in each TDD group are indicated by bold text and
dashed lines.
FIG. 13C illustrates a second embodiment of HARQ scheduling for UL
data transmission in an adaptive TDD system. In TDD Group #2-2, the
HARQ feedback for UL data transmission for UL subframes SF#2 and 7
should be transmitted in the DwPTS in SF#6 and 1, which is a common
special subframe in the TDD Group and will not be changed as a UL
subframe, as shown in Table 1340. In TDD Group #2-3, since there is
only one TDD configuration in this group, the HARQ feedback
operation for legacy UEs and new released UEs should be the same,
as shown in Table 1350.
If an HARQ NACK is indicated in the HARQ feedback for UL data
transmission, then UL data retransmission is expected. For a legacy
UE, similar to the UL data transmission, the UL data retransmission
should be transmitted in a common UL subframe. Once the HARQ NACK
is indicated in PHICH (Physical Hybrid-ARQ Indicator Channel), the
UL data retransmission timing should follow the UL grant table,
which is listed by Table 1210 (Table 8-2 in 36.213) in FIG.
12B.
For a legacy UE in TDD Group #1-1 (applying TDD configuration #3),
TDD Group #1-2 (applying TDD configuration #0), and TDD Group #2-1
(applying TDD configuration #3), the round trip time (RTT) of the
HARQ processes assigned to the legacy UE is 10 msec (e.g., 1 radio
frame=10 subframes), which means that a subsequent UL
retransmission subframe is the same as the first UL transmission
subframe. For TDD Group #2-3, the TDD configuration will not
change, the procedure keeps the same as current process.
However, for a legacy UE in TDD Group #2-2 (applying TDD
configuration #6), the UL data retransmission subframe is not
aligned with the first UL data transmission subframe due to the
HARQ RTT is not 10 msec. In this case, the UL data retransmission
may happen in an inconsistent subframe. To solve this problem, an
eNB may suppress the UL data retransmission.
FIG. 13D illustrates UL data retransmission in an adaptive TDD
system in accordance with one novel aspect. In the example of FIG.
13D, a legacy UE applying TDD configuration #6 in Group #2-2, and
its eNB assigns a UL grant in DL subframe SF#5 (1361). The UE
responses with UL data transmission in a subsequent UL subframe
SF#2 (1362). The HARQ feedback for the UL data transmission should
be replied in a subsequent DL subframe SF#6 (1363) from eNB to the
UE. If a NACK is indicated in PHICH in this case, then the UL
retransmission should be carried in UL subframe SF#3 (1365).
However, SF#3 is not a common UL subframe and may be changed to be
DL operation. A legacy UE may not be allowed to do the UL
transmission in this subframe if the current TDD configuration #6
is adapted to a different TDD configuration in TDD Group #2-2.
To solve this problem, eNB can suppress the UL retransmission in
SF#3 (1365) by sending an ACK in the previous SF#6 (1363), and
assign a UL grant with unchanged NDI (new data indicator) in the
next available assignment, for example, assign UL grant in subframe
SF#0 (1364) with unchanged NDI for UL retransmission. As a result,
the following processes can follow the process of UL data
transmission.
FIG. 14 is a flow chart of a method of adaptive TDD configuration
in a mobile communication network from eNB perspective in
accordance with one novel aspect. In step 1401, an eNB determines a
TDD group that contains multiple TDD configuration. In step 1402,
the eNB broadcasts TDD group information to a first legacy UE via a
system information block (SIB). In step 1403, the eNB broadcasts a
TDD reference configuration to the first UE via the SIB, where the
TDD reference configuration belongs to the TDD group. In step 1404,
the eNB transmits an instantaneous TDD configuration to a second
new released UE, where the instantaneous TDD configuration belongs
to the TDD group. In one embodiment, the multiple TDD
configurations in the TDD group have common subframes no less than
subframes #0, #1, #2 and #5, and the TDD reference configuration
has the most common uplink (UL) subframes as compared to other TDD
configurations in the TDD group.
FIG. 15 is a flow chart of a method of adaptive TDD configuration
in a mobile communication network from UE perspective in accordance
with one novel aspect. In step 1501, a UE receives TDD group
information that contains one or more TDD groups having multiple
TDD configuration. In step 1502, the UE receives a TDD reference
configuration that belongs to one of the TDD groups. In step 1503,
the UE performs measurements on DL subframes based on the TDD
reference configuration if the UE is a legacy UE, and performs
measurements on DL subframes based on an instantaneous TDD
configuration if the UE is a new release UE. In one embodiment, the
multiple TDD configurations in the TDD group have common subframes
no less than subframes #0, #1, #2 and #5, and the TDD reference
configuration has less common downlink (DL) subframes as compared
to other TDD configurations in the TDD group.
Although the present invention has been described in connection
with certain specific embodiments for instructional purposes, the
present invention is not limited thereto. Accordingly, various
modifications, adaptations, and combinations of various features of
the described embodiments can be practiced without departing from
the scope of the invention as set forth in the claims.
* * * * *